WPF Mediaelement LoadedBehavior does't work correctly? - wpf

Question

I am creating a simple app in WPF with VB.NET code behind. This code works perfectly. After the choosing of file, the function returns the correct numbers according to media type, the note image appears when the media is audio file and disappears when not. The media plays automatically. However I don't need to play the media automatically and when I set LoadedBehavior to Manual (instead of the default Play), strange things happen. The MediaOpened event is fired from time to time, the function returns sometimes zero, sometimes correct number, sometimes incorrect number. I am googling almost three days and I've found nothing. I'd like to make MediaElement.Play and MediaElement.Pause to show the first frame of video/image, but it's not possible without LoadedBehavior set to manual. I'd like to avoid LoadedBehavior somehow. Could someone give me a hint, please? Thank you very much in advance.
Private Sub btnFile_Click(sender As Object, e As RoutedEventArgs) Handles btnFile.Click
Try
Me.MediaElementSetting.LoadedBehavior = MediaState.Manual
Me.MediaElementSetting.UnloadedBehavior = MediaState.Close
Me.MediaElementSetting.Stop()
Me.MediaElementSetting.Close()
Me.PvwTimer.Stop()
Catch ex As Exception
'The exception occurs when LoadedBehavior is not set to manual, that's why it's unused
'MsgBox(ex.ToString)
End Try
Dim ArrayIndes as Integer = 1
OpenFileDialog(ArrayIndex)
End Sub
Sub OpenFileDialog(ByVal ArrayIndex As Integer)
Dim Dlg1 As New System.Windows.Forms.OpenFileDialog
Dlg1.ShowDialog()
If Dlg1.FileName <> "" Then
strFile = Dlg1.FileName
Me.MediaElementSetting.Source = New Uri(strFile, UriKind.RelativeOrAbsolute)
End If
End Sub
Private Sub MediaElementSetting_MediaOpened(sender As Object, e As RoutedEventArgs) Handles MediaElementSetting.MediaOpened
Dim t As Integer = AV()
End Sub
Function AV() As Integer
'Check, if the media has timespan (if it is image, audio, video w sound, video w/o sound - image has video without timespan)
If Me.MediaElementSetting.NaturalDuration.HasTimeSpan = True Then
If Me.MediaElementSetting.HasAudio = True Then
If Me.MediaElementSetting.HasVideo = True Then
'Media is a video with sound
MediaInfo = 4
Else
'Media is an audio
MediaInfo = 2
End If
Else
If Me.MediaElementSetting.HasVideo = True Then
'Media is a video without sound
MediaInfo = 3
End If
End If
Else
If Me.MediaElementSetting.HasVideo = True Then
'Media is an image
MediaInfo = 1
End If
End If
If MediaInfo = 2 Then
'Note is an image in a window. When the media is an audio it covers the mediaelement in a window
Note.Visibility = Visibility.Visible
Else
Note.Visibility = Visibility.Hidden
End If
Return MediaInfo
End Function

Answer 1

I'm not a VB.NET person, but here is a working example in C#.
Here's the XAML. I have a MediaElement, a Border as a stand-in for the notes image, and a button.
MainWindow.xaml
<Window x:Class="SO.MainWindow"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
xmlns:local="clr-namespace:SO"
Title="MainWindow"
Width="800"
Height="450">
<Grid>
<Grid.RowDefinitions>
<RowDefinition />
<RowDefinition Height="Auto" />
</Grid.RowDefinitions>
<MediaElement x:Name="MediaElementSetting"
Margin="16" />
<Border x:Name="AudioElement"
Margin="16"
Background="Red"
Visibility="Collapsed">
<TextBlock
HorizontalAlignment="Center"
VerticalAlignment="Center"
Foreground="White"
Text="AUDIO" />
</Border>
<Button x:Name="FileButton"
Grid.Row="1"
Margin="16"
Padding="8,4"
HorizontalAlignment="Right"
VerticalAlignment="Bottom"
Click="FileButton_OnClick"
Content="File" />
</Grid>
</Window>
Here's the code-behind.
I'm initializing the MediaElement once in the constructor of the window.
In order to show the first frame of the video, I need to set ScrubbingEnabled = true.
In OpenFileDialog(), after setting the Source I call SetupMedia which immediately calls Play, Pause, and then sets the Position. This ensures that the MediaOpened event gets called.
In the OnMediaOpened handler, I call GetMediaInfo which is like your AV function and instead of returning an integer, I return an enum instead.
MainWindow.xaml.cs
using System;
using System.Diagnostics;
using System.Windows;
using System.Windows.Controls;
using System.Windows.Forms;
namespace SO
{
public partial class MainWindow : Window
{
private bool isMediaOpened;
public MainWindow()
{
InitializeComponent();
MediaElementSetting.LoadedBehavior = MediaState.Manual;
MediaElementSetting.ScrubbingEnabled = true;
MediaElementSetting.UnloadedBehavior = MediaState.Close;
MediaElementSetting.MediaOpened += OnMediaOpened;
}
private void OnMediaOpened(object sender, RoutedEventArgs e)
{
isMediaOpened = true;
var mediaInfo = GetMediaInfo();
Debug.WriteLine($"{mediaInfo}");
}
private void SetupMedia()
{
MediaElementSetting.Play();
MediaElementSetting.Pause();
MediaElementSetting.Position = TimeSpan.FromSeconds(0);
}
private MediaInfo GetMediaInfo()
{
var mediaInfo = MediaInfo.None;
if (MediaElementSetting.NaturalDuration.HasTimeSpan)
{
if (MediaElementSetting.HasAudio)
{
mediaInfo = MediaElementSetting.HasVideo ? MediaInfo.VideoWithSound : MediaInfo.Audio;
}
else
{
if (MediaElementSetting.HasVideo)
{
mediaInfo = MediaInfo.VideoNoSound;
}
}
}
else
{
if (MediaElementSetting.HasVideo)
{
mediaInfo = MediaInfo.Image;
}
}
AudioElement.Visibility = mediaInfo == MediaInfo.Audio ? Visibility.Visible : Visibility.Collapsed;
return mediaInfo;
}
private void FileButton_OnClick(object sender, RoutedEventArgs e)
{
OpenFileDialog();
}
private void OpenFileDialog()
{
var dialog = new OpenFileDialog();
dialog.ShowDialog();
if (!string.IsNullOrEmpty(dialog.FileName))
{
if (isMediaOpened)
{
MediaElementSetting.Source = null;
isMediaOpened = false;
}
MediaElementSetting.Source = new Uri(dialog.FileName, UriKind.RelativeOrAbsolute);
SetupMedia();
}
}
public enum MediaInfo
{
None = 0,
Image = 1,
Audio = 2,
VideoNoSound = 3,
VideoWithSound = 4
}
}
}

Answer 2

Well, I accidentally found the solution, that works perfectly for me. To don't use MediaElement.LoadedBehavior = Manual at all
Private Sub MediaElementSetting_MediaOpened(sender As Object, e As RoutedEventArgs) Handles MediaElementSetting.MediaOpened
Dim t As Integer = AV()
Me.MediaElementSetting.UnloadedBehavior = MediaState.Close
Me.MediaElementSetting.LoadedBehavior = MediaState.Play
Me.MediaElementSetting.LoadedBehavior = MediaState.Pause
End Sub
And to control media with MediaElement.LoadedBehavior as well. This works for me perfectly, even when I think it's not correct. Logically, LoadedBehavior means loaded behavior.
Sub PlayMedia()
MediaElementSetting.LoadedBehavior = MediaState.Play
End Sub
Sub PauseMedia()
MediaElementSetting.LoadedBehavior = MediaState.Pause
End Sub
Sub StopMedia()
MediaElementSetting.LoadedBehavior = MediaState.Stop
End Sub